At present, a wide variety of fitness equipment for exercising muscles is present on the market, but basically can be classified into two categories, in which one uses the weight of an instrument to provide resistance; and the other uses a spring to provide the resistance. The existing arm exercisers using the springs to provide the resistance all adopt ordinary steel wire coil springs; due to limit of spring indexes (wire-diameter ratios) of the coil springs, when relatively great resistance needs to be provided, volumes of the coil springs may become relatively large, causing that the fitness equipment is relatively large in volume or relatively heavy in weight, thereby not only increasing manufacturing cost, but also resulting in inconvenience in storage and carrying.
In addition, most of the existing arm exercisers have a single function and is hard to achieve an effect of comprehensive exercise. Some arm exercisers having multiple functions often are manufactured by simply combining several different instruments, resulting in not only use inconvenience, but also reliability reduction.
For example, the China utility model patent CN203663337U discloses a multifunctional arm exerciser which can be used as an arm exerciser for exercising arm strength and can also be used as a chest expander for exercising chest muscles. The multifunctional arm exerciser comprises grip handles and first springs; sleeves with external threads are respectively fixed at both ends of the first springs; the grip handles arranged on the left and right are detachably arranged at both ends of the first springs for bearing bending moment through the threads, respectively, and constitute the arm exerciser; several annular first connection rings with buckle structures are respectively arranged on the two handles in a length direction; after removing the first springs from the two grip handles, a plurality of second springs sleeved inside the first springs are drawn out, and both ends of the second springs are connected with the opposite first connection rings on the two grip handles through annular second connection rings, so that the two grip handles and the second springs constitute the chest expander. In the patent, the coil springs are used as resistance elements, so large volume, security risk and other shortcomings also exist. In addition, when the multifunctional arm exerciser changes functions, the springs need to be disassembled and assembled again, causing use inconvenience.
For another example, the China utility model patent CN203220727U discloses a multifunctional arm exerciser which comprises an intermediate section spring, handles on both sides, and a protection rope; coiled opening-angle springs are connected to top ends of the handles on both sides; the other end of the coiled opening-angle springs are connected with handles of a grip exerciser; and the multifunctional arm exerciser can be used as an arm exerciser for exercising arm strength, and can also be used as the grip exerciser composed of the handle at one end, the spring and the handles, for exercising grip strength. Although the protection rope is arranged for improving security in the patent, other defects brought by the coiled springs still cannot be overcome. Moreover, the arm exerciser may also cause use inconvenience in such a manner that the grip exerciser is added on the handles.